Correlation of global and regional quantitative 99mTc-3,3-diphosphono-1,2 propanodicarboxylicacid single-photon emission computed tomography with echocardiography in patients with suspected transthyretin-related cardiomyopathy.

Aim
Quantitative single-photon emission computed tomography (SPECT) with 99mTc-3,3-diphosphono-1,2 propanodicarboxylicacid ([99mTc]Tc-DPD) is a cornerstone in the noninvasive diagnostic workup of amyloid transthyretin-related cardiomyopathy (ATTR-CM). As diagnosis is often suspected after transthoracic echocardiography (TTE), this study aims to explore the correlations between global and regional quantitative [99mTc]Tc-DPD SPECT results and TTE findings in patients with suspected ATTR-CM.Methods
Patients with suspected ATTR-CM from a single-center registry (B-CARE) were retrospectively included. All underwent quantitative [99mTc]Tc-DPD SPECT/CT at the baseline examination with calculation of standardized values [maximum standardized uptake value (SUVmax) and peak SUV (SUVpeak)], also normalized to bone activity (nSUVmax and nSUVpeak). Data on TTE, performed within 2 weeks from the DPD scintigraphy, were also collected.Results
One hundred forty four patients were included. Of these, 99 patients were eventually diagnosed with ATTR-CM. There was a significant correlation between septal (P ≤ 0.001) and lateral wall thickness (P = 0.004) and their respective, regional SUVs (P < 0.001 and P = 0.004, respectively), as well as global SUVs and maximum wall thickness (P = 0.024). Also, the presence of severe diastolic dysfunction correlated with nSUVs (P = 0.011).Conclusion
The robust correlation found between TTE-derived parameters and the corresponding [99mTc]Tc-DPD SPECT SUVs supports the link between morphologic alterations and [99mTc]Tc-DPD activity within the myocardium, also potentially highlighting a pathophysiological mechanism involved in the progression of ATTR-CM.